One confounding issue is that some are captive participants --that is someone is controlling their behavior (i.e. making them do it) via manipulation, threats and codependence, etc.
And that's kind of my point. It's not just financial situations, it's sometimes structural/societal situations that force them into that lifestyle. And if we supported people in shitty situations, we give them an "out" they wouldn't otherwise have, they wouldn't turn to something that they don't really want to do, that we as a society don't want them to do.
If we had systems in place that prostitues could turn to instead of prostitution, then only those that actually wanted to be a prostitue would be. People wouldn't turn to it as a last resort.